intrinsic nature, and continues to exist when I am not looking, or is
the table merely a product of my imagination, a dream-table in a very
prolonged dream? This question is of the greatest importance. For if
we cannot be sure of the independent existence of objects, we cannot
be sure of the independent existence of other people's bodies, and
therefore still less of other people's minds, since we have no grounds
for believing in their minds except such as are derived from observing
their bodies. Thus if we cannot be sure of the independent existence
of objects, we shall be left alone in a desert--it may be that the
whole outer world is nothing but a dream, and that we alone exist.
This is an uncomfortable possibility; but although it cannot be
strictly proved to be false, there is not the slightest reason to
suppose that it is true. In this chapter we have to see why this is
the case.

Before we embark upon doubtful matters, let us try to find some more
or less fixed point from which to start. Although we are doubting the
physical existence of the table, we are not doubting the existence of
the sense-data which made us think there was a table; we are not
doubting that, while we look, a certain colour and shape appear to us,
and while we press, a certain sensation of hardness is experienced by
us. All this, which is psychological, we are not calling in question.
In fact, whatever else may be doubtful, some at least of our immediate
experiences seem absolutely certain.

Descartes (1596-1650), the founder of modern philosophy, invented a
method which may still be used with profit--the method of systematic
doubt. He determined that he would believe nothing which he did not
see quite clearly and distinctly to be true. Whatever he could bring
himself to doubt, he would doubt, until he saw reason for not doubting